| Balance sheet location of derivative assets and liabilities and their related fair values (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010 | 
|---|---|---|
| Asset Derivatives | ||
| Asset Derivatives | $ 649 | $ 218 | 
| Liability Derivatives | ||
| Liability Derivatives | 208 | 141 | 
| Foreign exchange contracts | ||
| Asset Derivatives | ||
| Asset Derivatives | 166 | 36 | 
| Liability Derivatives | ||
| Liability Derivatives | 185 | 111 | 
| Interest rate contracts | ||
| Asset Derivatives | ||
| Asset Derivatives | 483 | 182 | 
| Liability Derivatives | ||
| Liability Derivatives | 23 | 30 | 
| Fair Value, Inputs, Level 2 | ||
| Asset Derivatives | ||
| Asset Derivatives | 649 | 218 | 
| Liability Derivatives | ||
| Liability Derivatives | 208 | 141 | 
| Fair Value, Inputs, Level 2 | Foreign exchange contracts | ||
| Asset Derivatives | ||
| Asset Derivatives | 166 | 36 | 
| Liability Derivatives | ||
| Liability Derivatives | 185 | 111 | 
| Fair Value, Inputs, Level 2 | Interest rate contracts | ||
| Asset Derivatives | ||
| Asset Derivatives | 483 | 182 | 
| Liability Derivatives | ||
| Liability Derivatives | 23 | 30 | 
| Fair Value, Inputs, Level 2 | Designated as Hedging Instrument | Foreign exchange contracts | Other current assets | ||
| Asset Derivatives | ||
| Asset Derivatives | 164 | 36 | 
| Fair Value, Inputs, Level 2 | Designated as Hedging Instrument | Foreign exchange contracts | Other Current Liabilities | ||
| Liability Derivatives | ||
| Liability Derivatives | 9 | |
| Fair Value, Inputs, Level 2 | Designated as Hedging Instrument | Foreign exchange contracts | Other non-current liabilities | ||
| Liability Derivatives | ||
| Liability Derivatives | 185 | 99 | 
| Fair Value, Inputs, Level 2 | Designated as Hedging Instrument | Interest rate contracts | Other Noncurrent Assets | ||
| Asset Derivatives | ||
| Asset Derivatives | 401 | 182 | 
| Fair Value, Inputs, Level 2 | Designated as Hedging Instrument | Interest rate contracts | Other non-current liabilities | ||
| Liability Derivatives | ||
| Liability Derivatives | 13 | 29 | 
| Fair Value, Inputs, Level 2 | Not Designated as Hedging Instrument | Foreign exchange contracts | Other current assets | ||
| Asset Derivatives | ||
| Asset Derivatives | 2 | |
| Fair Value, Inputs, Level 2 | Not Designated as Hedging Instrument | Foreign exchange contracts | Other Current Liabilities | ||
| Liability Derivatives | ||
| Liability Derivatives | 3 | |
| Fair Value, Inputs, Level 2 | Not Designated as Hedging Instrument | Interest rate contracts | Other Noncurrent Assets | ||
| Asset Derivatives | ||
| Asset Derivatives | 82 | |
| Fair Value, Inputs, Level 2 | Not Designated as Hedging Instrument | Interest rate contracts | Other non-current liabilities | ||
| Liability Derivatives | ||
| Liability Derivatives | $ 10 | $ 1 |